1. Soils Chapters 15 Living in the Environment, 15 th Edition, Miller Advanced Placement Environmental Science

3. Soils: Formation Soil horizonsSoil horizons Soil profileSoil profile HumusHumus O horizon Leaf litter A horizon Topsoil B horizon Subsoil C horizon Parentmaterial Mature soil Young soil RegolithRegolith BedrockBedrock Immature soil Fig. 10.12, p. 220

4. Soil Properties InfiltrationInfiltration LeachingLeaching Porosity/permeabilityPorosity/permeability TextureTexture StructureStructure pHpH 100%clayIncreasing percentage silt Increasing percentage clay 0 20 40 60 80 80 60 40 20 0 100%sand 80604020 100%silt Increasing percentage sand Fig. 10.16, p. 224 Water High permeabilityLow permeability Fig. 10.17, p. 224

5. TextureNutrientInfiltrationWater-HoldingAerationTilthCapacity ClayGoodPoorGoodPoorPoor SandPoorGoodPoorGoodGood Loam MediumMediumMediumMediumMedium

6. Soil Chemistry Acidity / Alkalinity – pH Acidity / Alkalinity – pH Major Nutrients Major Nutrients –Nitrogen –Phosphorus (phosphates) –Potassium (potash)

7. Acidity / Alkalinity – pH Proper pH directly affects the availability of plant food nutrients Proper pH directly affects the availability of plant food nutrients Soil is best if between pH 6 – 8 (except for certain acid loving plants) Soil is best if between pH 6 – 8 (except for certain acid loving plants) –‘Sour’ if too acidic –‘Sweet’ if too basic

8. Acidity / Alkalinity – pH Too acidic or basic will not Too acidic or basic will not –Allow compounds to dissolve –Allow presence of certain ions If soil is too acidic, add ground limestone If soil is too acidic, add ground limestone If soil is too basic, add organic material like steer manure If soil is too basic, add organic material like steer manure

9. Nitrogen Content Importance Importance –Stimulates above ground growth –Produces rich green color –Influences quality and protein content of fruit –A plant’s use of other elements is stimulated by presence of N Taken up by plant as NH 4 + and NO 3 - Taken up by plant as NH 4 + and NO 3 - Replenished naturally by rhizobacteria on legume roots Replenished naturally by rhizobacteria on legume roots Fertilizer from manure or Chemical rxn. Fertilizer from manure or Chemical rxn.

10. Phosphorus for Growth Abundant in Abundant in –Strong root system –Increases seed yield and fruit development –Parts of root involved in water uptake (hair) Major role in transfer of energy Major role in transfer of energy Taken up by plant as H 2 PO 4 - and HPO 4 -2 Taken up by plant as H 2 PO 4 - and HPO 4 -2 Fertilizer is made from rock phosphate Fertilizer is made from rock phosphate

11. Potassium Content Potash Potash Important in vigor and vitality of plant Important in vigor and vitality of plant –Carries carbohydrates through the plant –Improves color of flowers –Improves quality of fruit –Promotes vigorous root systems –Offsets too much N Found naturally in feldspar and micas Found naturally in feldspar and micas

12. Justus von Liebig’s Law of Minimum Plant production can be no greater than that level allowed by the growth factor present in the lowest amount relative to the optimum amount for that factor

13. Soil Formation Soils develop in response to Climate Climate Living organisms Living organisms Parent Material Parent Material Topography Topography Time Time

14. Climate Two most important factors that determine climate are Temperature and Moisture and they affect Two most important factors that determine climate are Temperature and Moisture and they affect –Weathering processes –Microenvironmental conditions for soil organisms –Plant growth –Decomposition rates –Soil pH –Chemical reactions in the soil

15. Parent Material Refers to the rock and minerals from which the soil derives. Refers to the rock and minerals from which the soil derives. The nature of the parent rock has a direct effect on the soil texture, chemistry and cycling pathways. The nature of the parent rock has a direct effect on the soil texture, chemistry and cycling pathways. Parent material may be native or transported to area by wind, water or glacier. Parent material may be native or transported to area by wind, water or glacier.

16. Topography Physical characteristics of location where soil is formed. Physical characteristics of location where soil is formed. –Drainage –Slope direction –Elevation –Wind exposure Viewed on Macro-scale (valley) or microscale (soil type in field) Viewed on Macro-scale (valley) or microscale (soil type in field)

17. Time After enough time, the soil may reach maturity. After enough time, the soil may reach maturity. –Depends on previous factors –Feedback of biotic and abiotic factors may preserve or erode mature profile.

18. Destructional -Weathering L andscapes broken down by chemical & physical processes & erosion Physical includes temperature changes (freezing and thawing, thermal expansion), crystal growth, pressure, plant roots, burrowing animals includes temperature changes (freezing and thawing, thermal expansion), crystal growth, pressure, plant roots, burrowing animals causes disintegration of parent material and facilitates chemical weathering causes disintegration of parent material and facilitates chemical weathering Chemical always in water includes hydration, hydrolysis, oxidation, reduction, carbonation and exchange examples : –oxidation of Fe to form limonite, deposited in joints, inhibits groundwater flow –hydrolysis of feldspars to form clay (kaolin) - forms infill for joints

20. Destructional - Mass wasting Gravitational movement of weathered rock down slope without aid of water or wind (landslips) Gravitational movement of weathered rock down slope without aid of water or wind (landslips) transported material is called colluvium transported material is called colluvium often set off by man’s activity often set off by man’s activity can involve very small to immense volumes of material can involve very small to immense volumes of material sliding, toppling, unravelling, slumping sliding, toppling, unravelling, slumping controlled by discontinuities (joints, bedding, schistocity, faults etc) controlled by discontinuities (joints, bedding, schistocity, faults etc)

22. Destructional - Erosion most significantly by running water Sheet erosion Sheet erosion –by water flowing down valley sides –severe when vegetation removed and geological materials uncemented Stream erosion Stream erosion –materials brought downslope by mass wasting and sheet erosion are transported by streams –erosion by the streams - meanders etc

24. Destructional - Karsts Forms by dissolution of limestone - limestone is only common rock soluble in water - dissolved carbon dioxide in rain water Forms by dissolution of limestone - limestone is only common rock soluble in water - dissolved carbon dioxide in rain water form highly variable ground conditions form highly variable ground conditions formation of sink holes - when buried leads to surface subsidence formation of sink holes - when buried leads to surface subsidence